Manganese alloy



June 16, 1942. R. s. DEAN MANGANESE ALLOY Filed July 1e, 193s um. Sw Svqw ww Q@ mw SQ mw ma 4P Patented `lune 16, 1942 MANGANESE ALLOY ReginaldS. Dean, Washington, D. C., assignor to Chicago Development Company,Chicago, Ill.

Application July 16, 1938, Serial No. 219,501

1 Claim.

My present invention relates to alloys containing manganese, iron andchromium, and is'flled as a continuation-impart of my prior copendingapplication Serial No. 199,329, filed April 1, 1938.

My present invention may be considered from several aspects, dependingupon the characteristics, properties and constitution of the alloyscoming within the range to which my invention relates. As an example, itmay be pointed out that so-called stainless steels of .the typecontaining 1B% chromium, 8% nickel and balance iron are not usable forall purposes. Where a considerable degree of hardness is desired, thistype of alloy cannot be used. If sufllcient amounts f carbon areintroduced, and the alloy is appropriately heat treated, a substantialhardening will result, but the stainless proporties are concomitantlylost. So-called stainless steels of this type are objectionable also incontaining a relatively expensive ingredient, namely nickel, which isrequired' to maintain the austenitic character of the alloy to which, inpart at least, is attributable its stainless properties. .Attempts havebeen made 4 to substitute manganese in whole or in part for the nickelin this type of alloy, and it is well known that alloys of manganese,chromium and iron are much more resistant to sulfur-containing gases andother forms of corrosion than other alloys which have been used for thepurpose. They seem to offer certain advantages over the 18-8 types ofalloys, but attempts to make truly stainless alloys of this characterhave not been satisfactory, particularly where other desirableproperties must be retained. For example, it was found that the chromiumcontent could not be raised sumciently to prevent scaling above 800degrees C. withcan be present without producing such extreme brittlenessas to result in the alloy being substantlally worthless for any lusefulpurpose. This brittleness was supposed to be due to the formation of thecompound ,FeCr. Even with lower amounts of,manganese, such as 15%, theprior art found it impossible to introduce more than approximately 15%of chromium without the occurrence. of brittleness. These considerationsare introduced entirely by way of illustration, and are adequate to showthe problems which the prior art faces in attempting to produce alloysof manganese, iron "and chromium having properties which would make themsuitable for employment in the same general fields in which other typesof ferrous alloys, stainless and otherwise, are :customarily employed.

I have found that by employing certain con-` centrations of iron,chromium and manganese, I can produce alloys of very remarkableproperties,

some of the important characteristics of which will be explainedhereinafter, and I have found also that these properties areparticularly obtainable within the range which I have established by theutilization of substantially pure manganese such as that prepared by theelectrolytic process as described in the U. S. Bureau of Mines Report ofInvestigations, No. 3322, or substantially pure manganese made by othermethods but approximating the product identiiled in purity. Thismanganese has the following typical composition: Fe, .00'7%; Si, .001%;Pb, .002%; Zn, .001%; Mo, .001%; Sn, .0005%; Cu, .0005%; Ni, .0005'%;Co, .0 005%; Ag, .0001%; As-f-Sb, .0001%; total Ti, A1, Zr, Cr, V, U,Be, Ta, Cb, P, and rare earths, '.001%; S, total, 0.276%; S, assulphide, .17% Mn, 99.7088%.

Manganese of this general typical composition may also be prepared bythe distillation of commercially pure manganese and by the utilizationof modified electrolytic processes, the nature of which need not`be setout for a full understanding of the present invention.

By the use of manganese of high purity and by means of appropriatetreatment for desulphurization, such as treatment with calcium carbide,metallic calcium and other agents, 1 have found it possible to productductile alloys having a cornposition up to about 17% chromium and 35%manganese with the balance substantially iron. Such alloys are malleableat elevated temperature, such as at 1200 degrees C., and, by coolingfrom this temperature to a temperature of 750 degrees C. and maintainingthem at this temperature for several hours, a permanently ductile alloyis obtained having great resistance to corrosion by sulphur-containinggases at elevated temperatures. f

Within the range which I have discovered, I have found it possible toVproduce hardenable stainless alloys, wherein there is a considerablerange'of ductility, a considerable range of hardening properties boththrough heat treatment and cold work, and a range of stainlessproperties, all as will be described hereinafter, enabling those skilledin the art to utilize iron-manganesechromium alloys in a Way and forpurposes which, as far as I know, have been impossible so far as priorart disclosures are concerned.

My invention may be considered with the accompanying drawing, in whichFig. 1 is a, ternary diagram on a relatively small scale, indicating thegeneral range in which the alloys Vof my present invention are found;and

Fig. 2 is a fragmentary portion of the ternary diagram of Fig. 1, withthe iron scale shown in a modiiied position, this diagram being ofsufiicient size sovthat the characteristics and properties of thevarious alloys may be readily deterthe reference character B, a dottedline beingdrawn between the two areas and having a significance whichwill be brought out hereinafter. The range of alloys with which mypresent invention is concerned is the entire range within the irregular.outline encompassing both the area A and the area B.

In my copending application above referred to, I disclose a range ofcomposition within the ternary system manganese, iron and chromium,where hardening of the alloys could be obtained by quenching from arelatively high temperature and then reheating to an intermediatetemperature, for example 500 degrees C. In that application, I offeredas a working hypothesis the suggestion that hardening was due, in therange so pointed out, to the separation of nely divided alpha manganesefrom the ternary solid solution which had been retained at roomtemperature or thereabouts by the quenching operation. I now find thathardening may also take place so far as I am now able to determine bythe sepalration of the compound FeCr.

For the purpose of simplication, I shall rst consider the invention sofar as it relates to alloys within the composition range marked "A.

Well C 60.

I find that the alloys Within this range are all ductile at hightemperatures, for example, 1200 degrees C., and remain ductile whenquenched in water from that temperature. I have found that thisductility, after quenching from a high temperature, is a sharp departurein behavior between alloys made in accordance with my invention andthose made with materials and methods heretofore known in the art.Quenched alloys within this composition range are magnetic and they arealso unstable with regard to heat treatment at elevated temperatures, sothat, on reheating to temperatures of the order of 500 degrees C. andabove, a pronounced hardening action takes place.

Under appropriate conditions of composition and temperature, hardness asgreat as Rockwell C 60 or more may lbe obtained. In general, the

maximum hardness is obtainable by heating for two hours at 700 degreesC. When such alloys are heated at temperatures above 700 degrees C.,

v, there is a gradually slight falling off in hardness until, atapproximately 800 degrees C., the hardness begins to fall olf rapidly.While all of these alloys are capable of being Ahardened by appropriateheat treatment, that is heat treatment appropriate to the particularcomposition utilized, not al1 of them may be given the maximum hardnesspossible due to the fact that some of them become so brittle as to bedisrupted if they are given drastic treatment, a phenomenon which Iexplain as due to the separation of too great an amount of the hardeningconstituent.

In general, if the proportion of chromium is not above 16%, considerableif not maximum hardness may be obtained without disruption, while alloyscontaining somewhat more than 16%, say up to 17%, of chromium may behardened Without disruption, providing the maximum hardness whichtheoretically might be obtainable be not attempted: For example, alloyscontaining more than 16% of chromium may be at 700 degrees C., a soundalloy containing more than 10% of chromium may be produced with ahardness on the Rockwell C scale of 38. As another example, -I may takea similar-alloy and quench it from 1200 degrees C. in a salt bath at 500degrees C., and obtain a hardness of Rock- This latter alloy, however,is somewhat more brittle than the lower chromium alloys having the samehardness.

For the purpose of more fully illustrating and describing my invention,I give below a group of illustrative examples which I have made comingwithin the composition range A of the ternary diagram. These examplesshow the change of magnetism .and hardness with various heat treatmentsand also indicate some of the results of cold work. In general, there'isan increase of from 18 to 20 hardness units on the Rockwell C scale. Itwill be observed also that the alloys which are magnetic as quenchedbecome nonmagnetic when subsequently reheated for hardening purposes,or, in any case, the magnetism is greatly reduced by the hardeningprocess. To

the metallurgist, these changes in magnetic properties are significantso far as structure of the ,alloy is concerned.

units) i. Magnetism quenched from 1200 degrees -1- C.-

appropriately hardened by quenching less drasticall'y than in water. Byquenching from 1200 degrees C. in oil, and reheating for one-half hour`Magnetism heat-treated at 700, degrees C. 2 hours Hardness quenched from1200" (Rockwell hardness).

Hardness after severe cold Work on the hammer- Hardness after heattreatment at '700 C. for 2 hours-C-GO.

Heat treatmentsafter quenching from 1200 -I- C.

EXAMPLE 2 Composition `Cr 16 Mn 32 Balance substantially iron.

Notes Treated with Co-brittle as cast.

Magnetism as cast-1.38 g./100 g.

Magnetism quenched from 1200 C.-57.0 g./

Magnetism heat treated at '100 C. for 2 hoursl 1.68 g./100 g. Hardnessas cast-C-15. Hardness from 1200" C-C-32.

Teat treatments-after quenching from 1200 C.+:

1 hour at 700 C.-C55 b hour at 750 C.-water quench-C-55. l/2 hour at 790C.-s1ow cool (air)-C55. V2 hour at 850 C.-slow cool (air)-C'41.

Magnetism as cast-0.35 g./ 100 g.

Magnetism quenched from 1200 C.-58 g./ 100 g.

Magnetism heat treated at 700 C. for 2 hours- Hardness quenched from1200 C.-C11.

Hardness cold worked-C-31.

Hardness after 700 C. heat treatment-cracked.

EXAMPLE 4 Composition Cr 15 Mn 30 Balance substantially iron.

Notes Ductile as cast.

Magnetism as cast-,4.54 g./ 100 g.

Magnetism quenched from 1200 C.-41 g./100 g.

Magnetism heat treated at 700 C. for 2 hours- Hardness quenched from1200 C.-C8.

Hardness after cold working-C-25.

Hardness after 1/2 hr. at 700 C.-C-47.

EXAMPLE 5 Composition Cr 16 5 Mn 33 Balance substantially iron.

Notes Brittle as cast. Desulphurized with Ca. Non-magnetic as cast.Quenched in water from 1200 C.-magnetic. Quenched in furnace at 700 C.from 1200 C.,

1 hr. in furnace-air cool--Rb-87. Oil quenched from 1200 C.-Rc-31.Heated at 700 C. for 1/2 hr.-air cool--Rc-38. Reheated to 1200 C.-waterquenched-H0430.

1/2 hr. at 700 C.-water quenched-Rc-30. 1/2 hr. additional-at 700C.-water quenched Rc-37 slight crack. 1/2 hr. additional at 700 C. waterquenchedcracked. Cooled on brick from 1200 C.-Rc40.

Heated to 700 C. 1/2 hr., air cooled-Rc-40. Heated to 1200 C., waterquenched-cold worked.

Heated to 700 C., 1/2 hr.cracked. Quenched from 1200 C. in salt bath at500 C. for 15 minutes, air cooled, supercial Rockwell C-60.

EXAMPLE 6 Composition Cr 18 niiiiii: 3?, Bfimewst- Remem-Bsancesubstantially ed addmg 1% cu Notes Very fine grained ascast-cannot be .cold worked. Hardness as cast-Rc-44.

Hardness annealed-Rb-96.

Hardness cold worked-Rc-28.

Hardness 500 C. Rc 26-magnetic pull 28.3. Hardness 600 C. Rc i4-magneticpull 3.44. Hardness 700 C. Rc L8-magnetic pull 2.8.

In connection with the alloys of my present invention, particularlythose of the area-A, I Wish to point out that their electricalresistance is relatively high and they are useful for heating elements,resistances and the like. In general, their electrical resistance isapproximately the same as nichrome and other wires in current use forresistance purposes. They have the advantage of having a melting pointabove 1200 C. and being highly resistant to scaling up to thistemperature.

While the properties of the alloys of my invention, and the manner inwhich results may be duplicated by no means require a full understandingof the hardening phenomenon, I wish to point out for the benet of thoseskilled in the art by hypothesis that hardening, particularly in thecase of those compounds in the area designated A, is due to a shift ofthe equilibrium from conditions where the phases are iron and ternarysolid solution to a condition where the phases are ternary solidsolution and the compound FeCr. I base my hypothesis on severalconsiderations and, in connection therewith, wish to point out that theternary solid solution and also the compound FeCr are well known topossess stainless properties to a high degree All of the compoundscomingwithin the area A are capable of hardening to a very appreciable extent,and all of them possess remarkable stainless properties, at least asstainless for most purposes as the 18-8 type of so-called stainlesssteel which is now extensively used where higher resistance to corrosionand adequate strength are desired.

The alloys falling within the designated area A may be utilized withmarked advantage in numerous elds. Thus, in addition to the usesreferred to hereinabove, they may be employed for bearings, cutlery,machine parts Where great wear resistance is required as in cams,ratchets, and the like. They may be utilized with excellent results forcooking utensils, for chemical equipment, for tools and dies, aselectrodes inl electrolytic operations,- for relatively non-magneticmachine parts, for fabrication requiring deep drawing characteristics,as thermostatic metals, for ornamental objects, and the like. They alsopossess the advantage of being readily welded. Their resistance tosulphur-bearing gases renders them useful for numerous purposes such asvalves for automotive engines, and the like. Other uses will readilysuggest themselves to those versed in the art in the light of aconsideration of their various properties as herein disclosed.

I give separate consideration to the range indicated by the characterB-in the drawing, because, Within this range, in my opinion, hardeningtakes place, for the most part, through the separation of manganese. Theproperties, however, are in many respects similar tol the properties ofthe alloys in area A, although there are denite difference in theproperties as well, particularly as the widely separated points in thetotal range disclosed are reached.

Like the alloys coming within the range A, the alloys Within thecomposition of the B range are all ductile or malleable at 1200 degreesC. and they are also malleable after quenching in water -from hightemperatures, such as 1100 to 1200 degrees C. They diier, however, fromthe alloys .in the composition range A in being substantiallynon-magnetic in the quenched state, although here also, as well beexpected, there is some gradation. They also differ from the alloys inthe composition range A by undergoing a greater degree of workhardening, the increase in hardness by the cold^work of the materialbeing in general of the order of 30% on the Rockwell C scale.

The alloys in the B range may be hardened by heating after quenching inwater from, for example 1200 degrees C. for short periods at 700 degreesC., or for longer periods at, for example, 500 to 600 degrees C. As a.further illustration of the characteristics of these alloys, I wish topoint out that they may be disrupted if heated for too long a time attemperatures of 700 degrees or thereabouts, and that this disruptingaction is accentuated by quenching from such temperatures. By quenchingless drastically, for example, quenching from 1200 degrees C. in a saltbath at about 00 degrees C., alloys in the B range may be obtained in amoderately hard l state, but without disruption.

To further illustrate my invention, I give below four specific examplesof the behavior of alloys coming Within the composition range marked B.It will be noted that the range encompassed within the area marked Bincludes as one of its limiting boundaries the pure iron-manganesealloys containing tfrom 34 to 38% iron, balance manganese Withnochromium.

EXAMPLE 7 Composition Cl 8 Mn 50 yBalance substantially i-ron.

Notes Ductile as cast.

Magnetism as cast-'0.11 g./l00 g.

Magnetism quenched from 1200 C. 0.58

g./l00 g.

Magnetism quenched from 700 C. heat treatment-0.49/100 g.

Hardness quenched from 1200 C. -C-7.

Hardness worked on air hammer-C-26. V2 hour at 700 C.-slow cool-C-42.

+1/'2 hour at 700 Cl.-slow coo1-C-42. Heated to 700 C.-quenched-brokeup.

ExAMPLE 8 Composition Cr 12 AMn 50 Balance substantially iron.

Notes Can be cold Worked as cast.

, Magnetism as 'cast-0.114 g./l00 g.

Magnetism quenched from 1l00 C.-1.78

g./l00 g.

Magnetism after 2 hours at 500 C.-2.5 g./ 100 gA Magnetism after 2 hoursat 600 C.-2.6 g./100 g.

Hardness Aquenched from 1100 C.-C9.

Hardness after 2 hours at 500" C.-C-l2.

EXAMPLE 9 Composition Mn 60 Balance substantially iron.

Notes EXAMPLE 10 Composition cr f 3.5 Mn 50 Notes Quenched in salt bathat 500 C. from 1200" C.-

15 minutes at 500 C air cooled-Hardness, Rockwell B-73.

Heated 1/2 hr. at 600 C. in salt bath, air cooled (does not ring),Rc-24.

` Heated 1/. hr. at '100 C. in salt bath-Rc- 24.

Heated l hr. additional at 700 C., air cooled.

. ing of 36% iron and 64% manganese having properties similar to thoseof the iron-chromium and manganese alloys and the character of thecurves shown in the drawing indicates clearly the relationship of thisalloy to the other alloys Hardness after 2 hours at 600 C.-toobrittledisrupted.

within the scope of the present -invention. It appears, therefore,that-/hardenable manganese alloys have a deilnite relationship to thehardenable iron-chromium manganese alloys., As an illustration, thealloy noted, namely the alloy of 36% iron, remainder manganese, isductile and non-magnetic as quenched from 1100 degrees C. Its Rockwellhardness in this condition is approximately C-3. On cold working, itshardness increases to approximately C-35, and by heating the quenchedalloy for thirty minutes at 600 degrees C., its hardness becomesapproximately C-56. These gures are illustrative of the results obtainedon relatively large numbers of samples.

In my prior copending application above r'eferred to, -I disclose thedesirable eiects of the additions of small amounts of nickel, copper,and titanium, and such substances, to alloys of iron, manganese andchromium. It should be understood that small amounts of these and otherelements including carbon may be added to the alloy compositions which Ihave disclosed without departing from the practice of my invention.

By the addition of such carbon as is introduced by employing calciumcarbide as a desulphurizer, the hardening of the alloys in Region A is.however, considerably lessened with some increase in ductility. While Iprefer to employ pure manganese of the character identified, certainphases of my invention may be practiced with fair results by the use ofmanganese containing not' substantially more than 1.0% of othermaterials. I have found, however, that markedly superior results areobtained with substantially pure manganese and its use is definitelypreferred. Such substantially pure manganese is preferably electrolyticmanganese, desulphurized preferably by the use of metallic calcium.

It will bev appreciated that the chromium and iron utilized in thealloys should be of sufficient purity so as not to introduce deleteriousamounts of other metals. Those versed in the art will, in the light ofmy teachings herein, readily be able to choose chromium and iron ofsumcient purity to accomplish the production of alloys fulfilling theobjects of my invention.

Thus it will be seen that I have discovered improved alloys ofmanganese, iron and chromium, the constitution of which may bedetermined by reference to the irregular area outlined in the drawing.Thus the chromium content may run up to 17% or slightly above, themanganese may range between approximately 25% and 65%, and the ironbetween about 43 and 67%. While these extreme ranges may be modiedslightly, Ain general it will be found that such modication will be atthe expense of desirable Properties. In the range, approximately 11.5to16% chromium and up to even 17.5% chromium, following suitableprecautions, with from approximately 25% to 43% manganese and 43% to 58%iron, a particularly desirable combination of properties is obtained,including extreme hardness .where desired, more than adequate ductilityand malleability for working, and unusual resistance to corrosion. Thisrange is, as before noted, in the general area marked with referencecharacter A. As we move down toward the lower right hand portion of theindicated area, particularly where we pass the region shown by thedotted lines, the properties show Variation, particularly in some lossof resistance to corrosion, with a concomitant decrease in hardening byheat treatment but with an increase in work hardening.

From the description of the alloys of my invention, those skilled in theart will understand at once the large number of uses to which they maybenapplied. It is suflicient to point out that the industrial uses arealmost unlimited 4where hardened stainless alloys are required. Theseare uses to which alloys of the same general type, that is to say,stainless alloys hardened without the use of carbon, have so far as Iknow never been applied before.

What I claim as new and desire to protect by Letters Patent of theUnited States is:

Alloys hardenable without cracking by heating, cooling and reheating toa lower temperature, said alloys consisting essentially of chromium,manganese and iron in the following proportions: from 6% to 12%chromium, from 50% lto manganese, and the balance iron, with theexception of such small amounts of impurities as will not affect theproperties of the alloys.

REGINALD s. DEAN'.

